Fabrication And Performance Optimization Of TiO₂Based Ultraviolet Detector

UV detection has exhibited tremendous prospects in astronomy, light-wavecommunications, environmental monitoring, imaging techniques, flame sensing, futurememory storage and modern integrated circuits. As we all know, UV detectors with highperformance, reliability and stability are urgently required in military and civilianapplications. Varies methods have been devoted to optimizing the performance of UVdetectors. Surface modification is a relatively efficient way to improve device performanceby reducing surface states and changing surface properties of the semiconductor materialsthrough some physical or chemical methods. Surface functionalization belongs to a kind ofsurface modification. Polymers are the most commonly used materials in functionalizedprocess. The functionalized materials always have higher light sensitivity and the surfacecharge transport characteristic is also changed. Besides, since doping and optimizing devicestructure can manipulate some electro-optical properties, such as conductivity, carriertransmission and light absorption characteristics, we can ingeniously utilize theseproperties to improve device performance.So far the type of wide band-gap oxide semiconductors which can be applied in UVdetector is very limited and the development of new composites is comparatively difficult.How to find an effective way making use of the existing materials to improve theperformance of UV detectors is the main content of this paper. In the paper, I providedthree proposals to investigate the methods of improving TiO2UV detector performance:modification on TiO2surface, Pt doping and optimizing device structure, different substrategrowth of TiO2nanowires.In chapter2, NH4+modified TiO2UV detector with Au electrodes was fabricated. Bydecreasing the number of exposed dangling bonds of oxygen atoms on TiO2surface, thebinding states which are similar to “dipoles” formed in the interface between Au electrodesand TiO2. The Schottky barrier height was reduced, eventually optimizing thecomprehensive performance of the device.In chapter3, high photoresponse TiO2UV detector was prepared via Pt doping of TiO2 thin film and optimizing device structure. The detailed structure of the device wasAu/TiO2(30nm)/Pt doping TiO2(150nm)/Au. On the one hand, Pt doped TiO2film as themain light sensitive layer of the device has smaller contact electric potential difference andlower barrier height with Au electrodes. On the other hand, thin TiO2film as the interfacemodified layer between Au electrodes and Pt doped TiO2layer, can further reduce thebarrier height. Thus the device exhibited high photocurrent, responsivity and fast responsetime.Chapter4mainly studied the effect of ITO and FTO substrates on the morphologies ofTiO2nanowire arrays (TNAs) and device performance. TNAs grown on FTO are highlyoriented with perpendicular to the substrate surface. TNAs grown on ITO exhibited growthtrend along all directions. Since the vertically ordered TNAs on FTO substrate can providea more favorable condition for charge transport, the photo-generated electrons can transmitfaster and more easily in the nanowires, thus the corresponding device exhibited moreexcellent photoelectric properties, indicating that compared with the cluster-shaped TNAson ITO, the well-aligned TNAs on FTO has more obvious superiority in the application ofUV detectors.